Camera shutter

ABSTRACT

A high speed focal plane shutter employs two panels each having an exposure aperture. The panels are arranged in spaced parallel relationship. A pair of flexible curtains is disposed between the panels. Each curtain is U-shaped. One end of each curtain is fixed to one of the panels, or the first panel, and the other end of each curtain is connected to a mouthpiece movable between open and closed positions, that is, the positions where the exposure aperture is respectively uncovered and covered by the curtain. A pair of link mechanisms is provided for respectively moving the mouthpieces along the inner surface of the other or second panel to open and closed positions. Each link mechanism includes a driving lever and a driven lever pivotally connected to each other. One end of each driving lever is pivoted on the first panel and the other end is slidably connected to one end of a mouthpiece. One end of each driven lever is slidably connected to the first panel and the other end is pivoted to the opposite end of the mouthpiece.

United States Patent [72] Inventor Takeo Ylmada Primary Examiner-SamuelS. Matthews Tokyo, Japan Assistant Examiner-Michael Harris [2|] Appl.No. 782,047 AttorneyHarry G. Shapiro [22] Filed Dec.9,1968 [45] PatentedSept. 28, 1971 [73] Assignee Nippon Kogaku K. K.

7 Tokyo, Japan ABSTRACT: A high speed focal plane shutter employs two[32] Priority Dee.'8, 1967, Dec- 8, 1967, Dec. 8, I967 panels eachhaving an exposure aperture. The panels are ar- [33] Japan ranged inspaced parallel relationship. A pair of flexible cur- I] l/ 42/735145and 2/78517 tains is disposed between the panels. Each curtain is U-shaped. One end of each curtain is fixed to one of the panels, [54]CAMERA SHUTTER or the first panel, and the other end of each curtaln iscon scmmsy 15 Drawing Figs nected to a mouthpiece movable between openand closed positions, that IS, the positions where the exposure apertureIS [52] US. Cl 95/57 respectively uncovered and covered by the curtain Apair of l l 1 CI G03, 9/28 link mechanisms is provided for respectivelymoving the [50] Field of Search 95/57 4 mouthpieces along h innerSurface f he other or second anel to 0 en and closed ositions. Each linkmechanism in- 156] References cued Eludes a dr i ving lever and a drivenlever pivotally connected to UNITED STATES PATENTS each other. One endof each driving lever is pivoted on the 2,4l7,482 3/1947 Gacki 95/57first panel and the other end is slidahly connected to one end 2,456,052l2/l948 Doyle et al. 95/57 ofa mouthpiece. One end of each driven leveris slidably con 2,526,432 5 SVeHS-SOH 95/57 nected to the first paneland the other end is pivoted to the op- 3,006,263 l0/l96l Elliott et al.95/57 posite end of the mouthpiece.

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( FC I ll 7 FIG. 14 4' 3 'l c T FC p 7 FIG. 15 3 \1 Ll mfilrmmmm 'l AC cI"* T FCI CAMERA suu'r'rsn -;The invention relates to an adjustable slitfocal-plane shutter for a. photographic camera, and more particularly toan improved form of curtain shutter capable of making exposures atexceedingly high speeds.

Conventional focal-plane shutters are so constructed that exposure isinitiated by winding up the first curtain covering the exposure windowaround the first cylinder by means of spring; and exposure is completedby winding up the string which is fitted to the second curtain in such amanner to render the second curtain to cover the exposure aperture,around the second cylinder by means of another spring; and

for preparation for the next exposure, the string fitted to the firstcurtain and the second curtain are restored to original positions bymeans of the third and fourth cylinders. Since each curtain is providedwith a cylinder on each end, comparatively strong force is required asthe spring force or brake force in order to accelerate or decelerate theinertia, in which is caused by the mass of curtains and strings andcaused by the inertia efficiencies of the cylinders produced whenopening or closing the curtains at a high speed. Moreover, since theseforces work to tension the curtains and strings having cylinders on bothends, both the curtains and the strings must have strength enough towithstand the said forces. It is impossible, therefore, to use extremelylight curtains and strings. Furthermore, since the tension strength iscomparatively great and the variation of the tension strength duringacceleration or deceleration is also large, the curtains are liable tostart vibration and generate high and strong operation sound when thecurtains are at nonrestraint position such as the exposure aperture.

It is an object of this invention to provide a focal plane shutter'notemploying strings and cylinders but employing link mechanism insteadwhich can have a small inertia efficiency compared with cylinders, andwhich does not give a large tension to the curtains and therefore makesit possible to construct a shutter with lightweight curtains whichreduces the force or the amount of work required to open or close thecurtains and at the same time minimizes the operation sound by dampingthe vibration generated when the curtains are positioned at the aperturesection.

In this invention a pair of curtains is used as the flexible curtain forthe camera shutter, as one end of the curtain is fixed, and the otherend is moved to open or close the exposure aperture. When metallicmaterials are used for the curtain, the curtain has a tendency to rollinto cylinder shape and, after assembly, the curtain is pressed againsta guide plate by the stress generated within the curtain to prevent thebuckling produced when one end of the curtain is moved to open or closethe exposure aperture.

Another object of this invention is to provide a camera shutteremploying a curtain with an element which functions to prevent thebuckling of the curtain by inoving in constant contact with theinnerside of the curved portion of the U- shaped curtain with thevibration absorbing element which moves to contact with the curtainwithin the exposure window when the curtain is at a position coveringthe exposure aperture and retreats with the certain retreats from theexposure aperture.

In this invention the driving device for the said camera shutter is socomposed that a second pin' is installed on another end of a first leverfixed on one sid 'of the exposure aperture frame with a first pin, thata fourth pin is planted on an end of second lever having at another enda third pin which fits to a first groove provided on the other side ofthe exposure aperture frame, that the first and second levers arepivotably joined to each other by a fifth pin, that the second pin isfitted slidable into a second groove provided on one end of a mouthpiecesecured to the movable end of the curtain, that the other end of themouthpiece is pivotally connected to the end of the second lever by thefourth pin, that the first through fourth pins are positioned at apiecesof a parallelogram through to each other and when their axes areprojected on a plane perpendicular to the shafts of the pins, the axesof the first, fifth and second pins are on a straight line and the axesof the third, fifth and fourth pins are also on another straight line,that distances between first and fifth pins, fifth and second pins,third and fifth pins, and fifth and fourth pins are identical, andfurther, that the lengthway directions of the first and second groovesare parallel to the straight line connecting the first and third pins.

In this invention, the cylinders having a large inertia efficiencycommonly used in conventional focal plane shutters are not employed and,instead the curtain stored in U-shape and a driving mechanism isprovided for moving the free end of the curtain, the driving mechanismbeing positioned between the flat or ar rnportions of the U-shapedcurtain Since this reduces the tension on the curtain considerably andenables a thinner curtain to be used, the weight of the curtain isreduced and, since the curtain is in U-shape and its free end is moved,the resistance caused by the inertia becomes small and, as afresult, thecapacity of driving device becomes small "and consequently the inertiaof the driving device itself also 5 caused by a small, drive force. Thisresults in the lower operation sound. Moreover, since it is possible toeffectively attenuate the vibration of the curtain, the operation soundcan be made lower. It is highly'advantageous to be enabled to constructan exceedingly high-speed shutter which is relatively small in size,light in weight and silent for portable cameras.

This invention will be described with reference to the drawings, inwhich:

FIG. 1 is a plan view of a shutter made in accordance with theinvention;

FIG. 2 Isa cross section showing the preexposure state of the shutter;

FIG. 3 is a cross section showing the state of the shutter duringexposure;

FIG. 4 is a cross section showing the post-exposure state;

FIG. 5 is a plan view of the shutter, the front panel and the spacers orprops being omitted for clarity in illustration;

FIG. 6 is a plan view of the leading curtain drive-link mechanism thecurtains and mouthpiece being omitted from this view for clarity inillustration.

FIG. 7 is a vertical side view of FIG. 6;

FIG. 8 is a horizontal side view of FIG. 6;

FIG 9 is an perspective view of FIG. 6;

FIG. 10 is a plan of link device prior to exposure;

FIG. 11 is a plan of link device during exposure FIG. 12 is a plan oflink device after completion of exposure; I

FIG. 13 is a stress-distribution diagram whenunformed material is used;

FIG. 14 is a stress-distribution diagram when formed material is used;and

FIG. 15 is a stress distribution diagram under accelerated state.

Referring to FIG. 1, 1 shows the front panel having an exposure apertureA and operates as a guide, 2 is a first or leading curtain covering A,and 4 is an element of a link mechanism driving the leading curtain 2.An element 4' is the element of a similar link mechanism driving asimilar trailing curtain 21 stored at the left of the device shown inFIG. 1 and beyond the exposure aperture A. FIG. 2 shows the preexposurestate wherein 2 and 2 are the leading and trailing curtains,respectively, 3 and 3' the mouthpicces fitted respectively to theleading curtain 2 and trailing curtain 2 by means of bonding etc., 4, 5,4' and 5' are elements of link mechanisms used respectively to drive theleading curtain and trailing curtain 6 an 6 are vibration absorbingelements, such as sponges or brushes, which are fitted to the members 5and 5 to engage the leading curtain 2 and the trailing curtain 2'; 7 isa rear panel also operating as a guide, and has an aperture A almost aslarge as the aperture A and is fixed to the front panel 1 by a spacer orprop 8. The leading curtain 2 and trailing curtain 2' are folded in U Ishape to provide curved portions B and B one of each is fixed to therear panel 7 at positions C and C.

FIG. 3 shows the state during exposure wherein the leading curtain 2 andits mouth piece 3 move parallelwise fromthe original positions to theright in the direction perpendicular to the base of the curved portionB, and lets the light beam pass through the exposure operature A andaperture A. FIG. 4 shows the postexposure state wherein the trailingcurtain 2' and mouth piece 3 move to cover the aperture A and theelement 6' moves to the vicinity of the center of the aperture, keepingcontact with the trailing curtain 2 In FIG. 5, D, D and E, E are theholds and oval grooves on the mouth pieces 3 and 3' respectively, and10, 10 are the pins planted respectively on the elements of linkmechanism driving the mouthpieces 3 and 3. These pins are linkedrespectively to holds D, D and grooves E, E The straight linesconnecting D, E and DEare respectively parallel to the base of thecurved portion and lengthwise directions of E, E are also parallel tothe base. A 1

FIGS. 6, 7, and 8 show the link mechanism used todrive the leadingcurtain 2. The state shown by dot-dash lines corresponds to FIG. 2 andthe state shown by solid lines corresponds to FIG. 3; and 4, 5, 11 an 12are levers. Lever 4 is pivotably connected to the rear panel 7 by meansof the planted pin 13, one end of which is the arm section F for input,

and the other end is linked with the groove E of the mouth piece 3 bymeans of the planted pin 10. Level 11 is fitted to lever 4 together withlever free to rotate by means of a pin 14, its one end is linked withthe hold D of the mouth piece 3 by means of the planted pin 9, and theother end is linked with the elongated groove G on the rear panel 7 bymeans of the planted pin 15. On the rear panel 7, the straight lineconnecting the pin 13 with the groove G is parallel to the base of thecurved portion B of the leading curtain and the lengthwise direction ofthe groove G is also parallel to the base of the curved portion. Onlever 4, the axes of the pins l3, l4 and onto the rear panel 7 arearranged in a straight line, the pin 14 being the middle point betweenthe pins 13 and 10. On lever 11, the axes of the pins 15, 14 and 8 ontothe rear panel 7 are arranged in a straight line, the pin 14 being themiddle point between the pins 15 and 9. The distance between the pins 15and, when projected onto the rear panel 7, pins 17, '16, 14 and' 13 forma parallelogram. The element 6 made of such shockabsorbing material assponge is bonded to the lever 5 at a place near the pin 14. The element6 can be bonded either to the pin 14 or, when the lever 5 is omitted asdescribed later, to lever 11 or lever 4.

Although omitted in FIG. 6, the link mechanism for driving the trailingcurtain is similar to the above-mentioned link mechanism for driving theleading curtain 2, the former being symmetrical with respect to thelatter. When the lever 4 is rotated, the straight line passing throughprojections of the pins 9 and 10 onto the rear panel 7 is parallel tothe straight line passing through the pin 13 and groove G and the pin 9moves along a straight line passing through the pin 13 and perpendicularto the straight line passing through the pin 13 and groove G, and themouthpiece 3 and the leading curtain 2 linked with the pin 9 open orclose the apertures A and A. In this case, since the mouth piece 3 issuspended at both ends by pins 9 and 10, deformation due to the loadcaused by inertia is reduced. The H section of lever,5 moves in parallelto the initial position and its right and left moving speed is equal tothe half of the moving speed of pins 9 and 10. Moreover, as is clearfrom FIG. 2, the moving speed of the mouthpiece 3 is identical with themoving speed of pins 9 and 10 and the right and left moving speed of thephase of the canned portion B of the leading curtain 2 is equal to thehalf of the moving speed of I the mouthpiece 3. Consequently, the Hportion of lever 5 moves always in contact with the inner side of thesection B to prevent the buckling otherwise produced on the flexibleleading curtain 2 when the leading curtain 2 and mouth piece 3 move inthe direction making an aperture. Since the shock-absorbing element 6 isfitted to a position near the pin 14, its right and left moving speed isclose to the half of the moving speed of the mouth piece 3 and, in astate that the leading curtain is covering the aperture, is in contactwith the leading curtain 2 at the aperture section or near the center ofthe unrestrained portion in the direction of the thickness of theleading curtain 2, and is so positioned as to attenuate the vibration ofthe curtain near the loop point, In the state the leading curtain 2 isstored, the shock-absorbing element 6 is also retreats from the aperturesection to be stored. During movement, the

thus serving always to attenuate the vibration of the leading curtain 2effectively.

FIG. 9 is a perspective view representing the relationship of eachelement, and the state represented by solid lines in FIG. 6 and part ofthe leading curtain 2 and mouth piece 3 is shown. FIGS. 10, 11, and 12show the states of the link mechanism before, during, andafter exposurerespectively.

The theoretical basis of the inertia of the curtain will be explained inthe following:

Referring to the inertia of the curtain that occupies a greater portionof the load on the drive device, when in general, making an aperture bymoving a single curtain in the direction of longitudinal direction ofthe aperture at a predetermined acceleration of a, the followingformulas are given, assuming the use of a curtain of minimum requiredarea,

W,= l=a m bl where V m is the mass of the curtain per unit area;

I is the length of the aperture;

b is the width of the aperture; t

f is the force required to drive an unfolded curtain (either wound in acylinder or plane); and

W, is the amount of work required for entire stroke.

On the other hand, when the same curtain is stored twicefolded, andassuming that F is the force required for driving the curtain; and W isthe amount of work required for entire stroke; then F amb(Zs/2) =amb(l9'l /4=) =3I4=ambl The formula (2) shows that in the present inventionthe amount of work required is small even when a curtain having thesamemass of the formula (1). Moreover, since in this invention, nocylinders are used at both ends of the curtain, and the curtain itselfforms the inertia load, the tension of the curtain is remarkably reducedand as a result, the curtain can be made of thin and light material, anthe relationship shown by the formula (2) is further improved greatly.

Next, when such materials having comparatively high coefficient ofelasticity and limit of elasticity and retaining the internal stress fora long period of time as metallic materials are i used to form thecurtain, it is possible by performing the curtain over the entire lengthby winding in the same direction as the bending section and byassembling the shutter, to reduce the stress at the bending section thanthe stress produced by using the unformed material, and to change thedistribution condition of the stress. This enables the curvature at thebending section to be taken larger and at the same time prevents theproduction of a concentrated pressure on the front panel 1 and rearpanel 7 near the bending section of the curtain and retains the tensionstress on the innerside of the flat portion of the curtain. FIGS. 13 and14 show in model form the distribution. conditionof stress at eachsection and the distribution condition of pressures on the front panel 1and rear panel 7 for each example of the case in which unformed materialis used and the case in which formed material is used, respectively. Inthese drawings, P denotes pressure, P, the tension strength F thecompression strength, and A the acceleration.

Furthermore, as illustrated in FIG. 15, a compression stress is producedon the portion moving to the right of the curtain due to the frictionbetween the curtain 2 and front panel 1 and to the inertia of eachsection of the leading curtain 2 when accelerating the leading curtain 2in the direction of making an aperture in other words in the directionof the bending section B by the mouthpiece 3. However, since the innerside of the flat portion of the curtain has been made previously toretain tension stress, the load is mainly supported by the outer portionof the cross section of the curtain and further since the action centerof gravity caused by the reaction of friction is positioned to the leftof the point shown in FIG. 13 and works to reduce the distance betweenthe working points, the curtain which is thin compared with the lengthnever produces a buckling. As has been stated so far, the levers 5 and12 used for preventing buckling can be omitted when metals or othermaterials are formed and used as the material of the curtain.

What is claimed is: l. A high-speed focal-plane shutter for aphotographic camera comprising a first panel and a second panel eachhaving an exposure aperture, the panels being arranged in spaced,

parallel relationship, a pair of flexible curtains disposed between thepanels and symmetrically arranged with respect to each other, eachcurtain being U-shaped one end of each curtain being fixed to the firstpanel and the other end of each curtain being connected to a mouthpiecemovable between open and closed positions, and a pair of link mechanismsfor respectively moving the mouthpieces along the inner surface of thesecond panel to open and closed positions, the link mechanisms beingsymmetrical with respect to each other,

each link mechanism including a driving lever and a driven leverintersecting and pivotally connected to each other, one end of eachdriving lever being pivoted on the first panel and the other end beingslidably connected to one end of a mouthpiece, one end of each drivenlever being slidably connected to the first panel and the other endbeing pivoted to the opposite end of the mouthpiece, the levers beingretractable into their respective U-shaped curtains when the mouthpieceis moved to open position. v

2. A high-speed focal-plane shutter according to claim 1; wherein thefirst panel has a pair of guide grooves extending parallel to the edgeof the mouthpiece and are provided on the opposite side to the drivinglever pivoted portion, the driving lever having a pin fitted into theguide groove.

3. A high-speed focal-plane shutter according to claim 2, wherein themouthpiece has a groove at one end thereof, and the driving lever has apin fitted into said groove.

4. A high-speed focal-plane shutter according to claim 3; wherein thedriven lever is S-shaped, whereby the mouthpiece may pass over saidguide groove and the pivoted portion of the driving lever. l

5. A high-speed focal-plane shutter according to claim I includingvibration-absorbing elements provided near the pivotal connection toeach other of the driving and driven levers in engagement with the innersurfaces of the curtains.

6. A high-speed focal-plane shutter according to claim I, in-

' cluding means for preventing buckling of the curtains, said cludingvibration-absorbing elements provided on said ivotable member mengagement w|th the inner surfaces of t e curtain.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Pa 3,603,463 DatedSeptember 28, 1971 Inventor(s) eO Yamada It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Column 5, line 32, a comma should be inserted after "U-shaped";

Column 6, line 13, "driving" (second occurrence) should read drivenSigned and sealed this 26th day of September 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents uscoMM-Dc 60376-P6D n U 5. GOVERNMENT PRINTING DFFICEI l9.O-'55"3l

1. A high-speed focal-plane shutter for a photographic camera comprisinga first panel and a second panel each having an exposure aperture, thepanels being arranged in spaced, parallel relationship, a pair offlexible curtains disposed between the panels and symmetrically arrangedwith respect to each other, each curtain being U-shaped, one end of eachcurtain being fixed to the first panel and the other end of each curtainbeing connected to a mouthpiece movable between open and closedpositions, and a pair of link mechanisms for respectively moving themouthpieces along the inner surface of the second panel to open andclosed positions, the link mechanisms being symmetrical with respect toeach other, each link mechanism including a driving lever and a drivenlever intersecting and pivotally connected to each other, one end ofeach driving lever being pivoted on the first panel and the other endbeing slidably connected to one end of a mouthpiece, one end of eachdriven lever being slidably connected to the first panel and the otherend being pivoted to the opposite end of the mouthpiece, the leversbeing retractable into their respective U-shaped curtains when themouthpiece is moved to open position.
 2. A high-speed focal-planeshutter according to claim 1; wherein the first panel has a pair ofguide grooves extending parallel to the edge of the mouthpiece and areprovided on the opposite side to the driving lever pivoted portion, thedriving lever having a pin fitted into the guide groove.
 3. A high-speedfocal-plane shutter according to claim 2; wherein the mouthpiece has agroove at one end thereof, and the driving lever has a pin fitted intosaid groove.
 4. A high-speed focal-plane shutter according to claim 3;wherein the driven lever is S-shaped, whereby the mouthpiece may passover said guide groove and the pivoted portion of the driving lever. 5.A high-speed focal-plane shutter according to claim 1, includingvibration-absorbing elements provided near the pivotal connection toeach other of the driving and driven levers in engagement with the innersurfaces of the curtains.
 6. A high-speed focal-plane shutter accordingto claim 1, including means for preventing buckling of the curtains,said means including a pivotable member for each curtain, an end of eachmember being engageable with the inner surface of each U-shaped curtainat the curved base thereof.
 7. A high-speed focal-plane shutteraccording to claim 6; wherein said pivotable member is T-shaped and actsas one link in a parallelogram for cooperation with said driving lever.8. A high-speed focal-plane shutter according to claim 7, includingvibration-absorbing elements provided on said pivotable member inengagement with the inner surfaces of the curtain.